Electronic devices employing aligned organic polymers

ABSTRACT

The devices can be fabricated by a method that permits active polymer chains to be polymerized on the surface of an electrode such that the active polymer chains are aligned with one another. The active polymer chains can also be covalently linked to a second electrode so the active polymer chains are located in an active layer of the device. The polymerization method can be paused and resumed at any point in the polymerization so nanoparticles can be added into the active layer. Additionally, the polymerization method allows that active polymer chains to be polymerized so they include junctions such as p-n junctions and Schottky junctions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. Nos. 61/643,786, filed on May 7, 2012, and 61/678,484,filed on Aug. 1, 2012, the disclosure of which are incorporated hereinin their entireties.

FIELD OF THE INVENTION

The invention relates to organic semiconductors, and more particularly,to electronic devices that employ organic semiconductors.

BACKGROUND

Organic semiconductors can be used to fabricate a variety of electronicdevices. These devices can often generate electricity from incidentlight as occurs in photovoltaic devices such as solar cells. Thesedevices often include one or more layers of material that include one ormore organic semiconductor(s). The efficiency of these devices can oftenbe increased by increasing the charge carrier mobility within theselayers. However, the organic semiconductors that are currently used inthese devices are generally highly disorganized. This disorganizationrequires that charge carriers jump from one strand of the organicsemiconductor to another strand in order to travel though the layer ofmaterial. As a result, this disorganization is a source of inefficiencyin these devices. There is a need for an increased efficiency in devicesthat employ organic semiconductors.

SUMMARY

An embodiment of the electronics device includes a first electrode and asecond electrode. The device also includes organic polymer chains thatare each covalently linked to both the first electrode and the secondelectrode.

Another embodiment of the electronics device includes block copolymerchains that are aligned with one another and that are fabricated on asurface of an electrode. The block copolymer chains each include a firstblock of a first organic polymer. The block copolymer chains alsoinclude a second block of a second organic polymer. In some instances,the first organic polymer is a semiconducting polymer acts as anelectron acceptor and the second organic polymer is a semiconductingpolymer acts as an electron donor. The block copolymer can be a diblockcopolymer or can include more the two blocks. A p-n junction can beformed at an interface between the first block and the second block.

In some instances, the device includes nanoparticles positioned suchthat the block copolymer chains extend through interstices between thenanoparticles. In some instances, a p-n junction is formed at theinterface of the first block and the second block and the nanoparticlesare positioned such that the p-n junction is positioned in theinterstices between the nanoparticles.

In some instances, the device is a solar cell.

A method of forming the device includes polymerizing a polymer on anelectrode so as to form chains of the polymer on the electrode. Themethod also includes pausing the polymerization after the polymerizationhas been started. The method further includes applying a layer ofnanoparticles to the portion of the polymer chains that were formedbefore the polymerization was paused. The method additionally includesresuming the polymerization of the polymer after applying thenanoparticles. In some instances, the polymerization is resumed suchthat the polymer chains extend through interstices between thenanoparticles.

Another embodiment of the method includes fabricating block copolymerchains on the surface of the electrode. Fabricating the block copolymerchains on the electrode can include polymerizing the block copolymerchains on the electrode. Polymerizing the block copolymer chains caninclude performing a ring-opening polymerization such as a Ring-OpeningMetathesis Polymerization. In one example, the block copolymer chainsare polymerized by a Surface Initiated Ring-Opening MetathesisPolymerization.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross section of an electronics device that employs organicspolymers in an active layer of the device.

FIG. 2 provides an example of a portion of a device constructedaccording to FIG. 1.

FIG. 3 is a cross section of an electronics device constructed accordingto FIG. 1 but with nanoparticles introduced into the active layer of thedevice.

FIG. 4 illustrates an active layer that is formed on an electrode and issuitable for incorporation into other devices.

FIG. 5 illustrates a method of fabricating the device of FIG. 1 throughFIG. 4.

DESCRIPTION

As used herein and in the appended claims, the singular forms “a,”“and,” and “the” include plural referents unless the context clearlydictates otherwise. Thus, for example, reference to “a pillar” includesa plurality of such pillars and reference to “the catalyst” includesreference to one or more catalysts known to those skilled in the art,and so forth.

Also, the use of “or” means “and/or” unless stated otherwise. Similarly,“comprise,” “comprises,” “comprising” “include,” “includes,” and“including” are interchangeable and not intended to be limiting.

It is to be further understood that where descriptions of variousembodiments use the term “comprising,” those skilled in the art wouldunderstand that in some specific instances, an embodiment can bealternatively described using language “consisting essentially of” or“consisting of.”

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which this disclosure belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice of the disclosed methods and compositions, the exemplarymethods, devices and materials are described herein.

The publications discussed above and throughout the text are providedsolely for their disclosure prior to the filing date of the presentapplication. Nothing herein is to be construed as an admission that theinventors are not entitled to antedate such disclosure by virtue ofprior disclosure.

By “about” is meant a quantity, level, value, number, frequency,percentage, dimension, size, amount, weight or length that varies by asmuch as 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2 or 1% to a referencequantity, level, value, number, frequency, percentage, dimension, size,amount, weight or length. With respect to ranges of values, thedisclosure encompasses each intervening value between the upper andlower limits of the range to at least a tenth of the lower limit's unit,unless the context clearly indicates otherwise. Further, the inventionencompasses any other stated intervening values. Moreover, the inventionalso encompasses ranges excluding either or both of the upper and lowerlimits of the range, unless specifically excluded from the stated range.

A method of fabricating electronics devices such as solar cells isdisclosed. The method permits active polymer chains to be polymerized onthe surface of an electrode such that the active polymer chains arealigned with one another. The active polymer chains can include a blockcopolymer where a first block of the copolymer acts as an electronacceptor and a second block of the copolymer acts as an electron donor.

Since the active polymer chains are aligned with one another, theopposing ends of the active polymer chains can be concurrently attachedto two electrodes. As a result, an electron traveling along an activepolymer chain can reach either electrode without the need for chainhopping. The elimination of the need for chain hopping provides for amore efficient device. When the active polymer includes a blockcopolymer, the first block can be covalently bonded directly to thesecond block so a p-n junction can be formed at the interface betweenthe first block and the second block. The covalent bonding between thefirst and second blocks allows efficient transfer of electrons betweenthese domains.

A possible method of fabricating the device includes polymerizing theactive polymer chains on an electrode that will become part of thedevice. The polymerization can be paused at nearly any point in thereaction and then resumed. A layer of nanoparticles can optionally beformed on the partially formed active polymer chains while thepolymerization is paused. When the polymerization is resumed, the activepolymer chains can extend through interstices in the nanoparticles. Theability to pause the polymerization at nearly any point in thepolymerization allows one or more layers of the nanoparticles to bepositioned anywhere along the length of the active polymer chains. Forinstance, a layer of the nanoparticles can be positioned such that thep-n junctions are positioned in the interstices of the nanoparticles.Additionally, the nanoparticles can be selected to scatter incidentlight. When the nanoparticles are positioned to scatter this light nearthe p-n junctions, the amount of light absorbed near the p-n junctionscan be increased in order to further enhance the efficiency of thedevice. In addition to scattering light or as an alternative toscattering light, the nanoparticles can increase optical density nearthe nanoparticles as a result of the nanoparticles behaving as anantenna. When the nanoparticles are positioned to enhance light densitynear the p-n junctions, the amount of light absorbed near the p-njunctions can be increased in order to further enhance the efficiency ofthe device.

FIG. 1 is a cross section of an electronics device that employs organicpolymers. The device includes an active layer 10 between a firstelectrode 12 and a second electrode 14. The active layer 10 includes afirst anchoring group 16 that attaches a first organic polymer 18 to thefirst electrode 12. The active layer 10 also includes a second anchoringgroup 20 that attaches a second organic polymer 22 to the secondelectrode 14. In some instances, the first anchoring group 16 iscovalently bonded to both the first electrode 12 and to the firstorganic polymer 18 and/or the second anchoring group 20 is covalentlybonded to both the second electrode 14 and to the second organic polymer22. In some instances, the first anchoring group includes covalent bondsarranged such that the first organic polymer 18 is covalently linked tothe first electrode and/or the second anchoring group includes covalentbonds arranged such that the second organic polymer 22 is covalentlylinked to the second electrode. For instance, a pathway from the firstelectrode to the first organic polymer 18 can extend through the firstanchoring group along only covalent bonds and/or a pathway from thesecond electrode to the second organic polymer can extend through thesecond anchoring group along only covalent bonds.

The first organic polymer 18 is bonded directly to the second organicpolymer 22. The first organic polymer 18 can be covalently bondeddirectly to the second organic polymer 22. When the first organicpolymer 18 and the second organic polymer 22 are covalently bonded toone another, the active polymer 24 can be a block copolymer. Forinstance, the first organic polymer 18 can be a first block of a blockcopolymer that includes two or more blocks and the second organicpolymer 22 can be a second block of the block copolymer.

The first electrode 12 and/or the second electrode 14 are electricallyconducting substrates and can be single layer or can include multiplelayers of material. Suitable materials for a layer of the electrodesincludes, but is not limited to, metals such as aluminum, silver, andcopper. In some instances, one or more of the electrodes includes alayer of a metal oxide on the surface of the metal. One or both of theelectrodes can be transparent or substantially transparent to lighthaving wavelengths relevant to photovoltaics and photodiodes,approximately 200-2000 nm in freespace. An example of an opticallytransparent material that is suitable for use as a layer of an electrodeincludes, but is not limited to, fluorine tin oxide (FTO) or fluorinedoped tin oxide or indium doped tin oxide.

The first anchoring group 16 and/or the second anchoring group 20 can bea typical anchoring groups used to attach a polymer to a surface such asphosphonates, carboxylates, silanes, thiols, nitrites, carbenes,isocyanates, amines, or catechols. The first anchoring group 16 and/orthe second anchoring group 20 can be optional. For instance, the firstorganic polymer 18 can be attached directly to the first electrode 12and/or the second organic polymer 22 can be attached directly to thesecond electrode 14 using techniques such as hydrosilylation,hydrolysis, or metathesis.

Suitable first organic polymers 18 include polymers that are electronacceptors and/or semiconducting organometallic polymers that areelectron acceptors. These types of polymers can be p-type semiconductorsand/or can be doped to behave as p-type semiconductors. Suitable secondorganic polymers 22 include polymers and/or semiconductingorganometallic polymers that are electron donors or emitters. Thesetypes of polymers can be n-type semiconductors and/or can be doped tobehave as an n-type semiconductor. Organic polymers that are suitablefor use as the first organic polymers 18 and/or the second organicpolymers 22 are polymers that exhibit semiconductor properties and thathave a backbone where the monomers include or consist of carbon.Examples of polymers that can serve as the first organic polymer 18and/or second organic polymer 22 include, but are not limited to,polyacetylenes, polypyrroles, polyanilines, poly(thienylenevinylene)s,polythiophenes, and poly(phenylenevinylenes), any of which can besubstituted or unsubstituted and/or branched or unbranched. An exampleof a polymer that can be doped includes, but is not limited to,polyacetylenes. Organometallic semiconductor polymers are polymers thatexhibit semiconducting properties and include carbon, hydrogen, and ametallic coordination complex that can be located in the backbone and/orsidechains. The metal from the coordination complexes can interrupt theconnectivity of the organic backbone. Examples of organometallicsemiconductor polymers that can serve as the first organic polymer 18and/or second organic polymer 22 include, but are not limited to,platinum bridged organometallic polymers.

FIG. 2 provides an example of a portion of a device constructedaccording to FIG. 1. The illustrated device is a photovoltaic devicesuch as a solar cell. The first electrode 12 is transparent to incominglight. For instance, a layer of FTO 26 can serve as the first electrode12. The layer of FTO transmits the incoming light and is electricallyconductive. As is evident from FIG. 2, the electrode can be deposited ona transparent substrate 28 such as a SiO₂ substrate. The secondelectrode 14 need not be transparent to the light and can optionally beconstructed to reflect incident light back into the active layer 10. Thesecond electrode 14 includes a layer of aluminum oxide 30 on a layer ofaluminum 32.

The first anchoring groups and the second anchoring groups 20 shown inFIG. 2 result from covalently bonding a phosphonic acid directly to thefirst electrode 12 and the second electrode 14. A suitable phosphonicacid for acting as a precursor to the illustrated anchoring groupsincludes, but is not limited to, CH₂CH(CH₂)_(x)PO(OH)₂. In FIG. 2, thevariable x or y is greater than or equal to 1 and/or less than 20. Inone example, x is 1 and y is 1.

The active polymer 24 is a block copolymer that includes two blocks. Oneof the blocks includes polyacetylene and the other block includespoly(thienylenevinylene). The polyacetylene serves as an electronacceptor and the poly(thienylenevinylene) serves as an electron donor.In FIG. 2, the variable n can be greater than or equal to 5 and/or lessthan or equal to 10,000 and the variable m can be greater than or equalto 5 and/or less than or equal to 10,000. The polyacetylene iscovalently bonded directly to the poly(thienylenevinylene) toeffectively provide a p-n junction at the interface of the first organicpolymer 18 and the second organic polymer 22.

As evident from FIG. 2, a pathway from the first electrode to the firstorganic polymer 18 extends through the first anchoring group 16 alongonly covalent bonds and a pathway from the second electrode to thesecond organic polymer extends through the second anchoring group 20along only covalent bonds. Accordingly, the first organic polymer 18 iscovalently linked to the first electrode and the second organic polymer22 is covalently linked to the second electrode.

As illustrated in FIG. 3, a layer 34 of nanoparticles 36 can beintroduced into the active layer 10. Examples of suitable nanoparticles36 include, but are not limited to, nanoparticles 36 that scatterincident light. Scattering of incident light can increase lightabsorption by the semiconductors. The increased absorption of light inthe semiconductor can increase the efficiency of the certain devicessuch as solar cells. Further, the nanoparticles 36 can be locally placedat one or more locations within the active layer 10 that furtherincrease the efficiency of the device. For instance, the nanoparticles36 can be placed at or near the interface between the first organicpolymer 18 and the second organic polymer 22. As a result, thenanoparticles 36 can be placed at or near the p-n junction that ispresent at this interface in order to increase carrier generation nearthe p-n junction, which is highly desirable for the purposes ofefficiency.

In some instances, the nanoparticles 36 are not bonded to the activepolymer 24. For instance, there are not covalent bonds between thenanoparticles 36 and the active polymer 24. Alternatively, functionalgroups could be added to the polymer and/or nanoparticles to createcovalent bonds between the nanoparticles and the polymer. Examples ofsuitable nanoparticles 36 include, but are not limited to, metals ormetal oxides such as metals that include or consist of one or morecomponents selected from the group consisting of titania, silver, gold,aluminum, alumina, and silica. Suitable diameters for the nanoparticles36 include, but are not limited to, diameters greater than 5 nm, 10 nmor 100 nm and/or less than 1000 nm.

The device of FIG. 1 and FIG. 3 is disclosed in the context of aphotovoltaic device such as a solar cell. However, the illustratedarrangement can be applied to other devices. Examples of other devicesthat can employ the disclosed arrangement include diodes, capacitors,light-emitting diodes (LEDs), transistors, photodetectors, chemicalsensors, and thermoelectrics. Further, these devices can also beconstructed using only a portion of the illustrated arrangement. Forinstances, these devices can incorporate the device disclosed in thecontext of FIG. 1 through FIG. 3 but with the disclosed device excludingthe second electrode 14 or excluding both the second electrode 14 andsecond anchoring group 20 as illustrated in FIG. 4. Alternately, thesedevices can incorporate the device disclosed in the context of FIG. 1through FIG. 3 but with the disclosed device excluding the firstelectrode 12 or excluding both the first electrode 12 and firstanchoring group 16. Although FIG. 4 illustrates the active layer 10including nanoparticles 36, the active layer 10 can exclude thenanoparticles 36.

In the device illustrated in FIG. 1 through FIG. 4, the active polymerchains 24 are aligned with one another. For instance, the active polymerchains 24 each extends away from the first electrode 12 and/or thesecond electrode 14 in the same direction. An end-to-end vector canprovide a measure of this alignment. An end-to-end vector can beillustrated as an imaginary line drawn between the terminal carbons inthe backbone of the active polymer chains 24 can provide a measure ofthis alignment. Alignment is achieved when these lines are parallel orsubstantially parallel to one another. For instance, each line can havean angle relative to the first electrode (θ₁) or relative to the secondelectrode (θ₂). Accordingly, the collection of lines can have an averageangle between each line and the first electrode (θ_(1,avg)) or thesecond electrode (θ_(2,avg)). The active polymer chains 24 can bealigned such that more than 50%, 75%, or even 90% of the active polymerchains 24 have an angle relative to the first electrode (θ₁) that iswithin the angle (θ_(1,avg))+/−30°, 15°, or 5°. Additionally oralternately, the active polymer chains 24 can be aligned such that morethan 50%, 75%, or even 90% of the active polymer chains 24 have an anglerelative to the second electrode (θ₂) that is within the angle(θ_(2,avg))+/−30°, 15°, or 5°. In some instances, the active polymerchains 24 are fabricated such that the end-to-end vectors areperpendicular or substantially perpendicular to the first electrode orthe second electrode. In these instances, the value of (θ_(1,avg))and/or (θ_(2,avg)) can be 90°.

The first organic polymer and the second organic polymer are disclosedabove as being semiconductors and as providing a p-n junction, however,the electronic device can have other constructions. As an example, thefirst organic polymer and/or the second organic polymer can be selectedto provide a Schottky junction. This Schottky junction can be formedeither between the two blocks of a diblock copolymer, or at thepolymer/electrode interface. For instance, the first organic polymer orthe second organic polymer can be a semiconductor as disclosed above andthe other organic polymer can be an organic polymer that is doped to bemetallic or semi-metallic in that there is no band-gap or a very smallband-gap which leads to higher electrical conductivity. Alternately, thefirst organic polymer and the second organic polymer can be the samesemiconducting polymer but one of them can be doped so as to be metallicor semi-metallic. Additionally, the first and second organic polymer maybe different polymers of the same type (for example, both p-type), withthe rectifying junction being a polymer/electrode Schottky contact. Anexample of an organic polymer can be doped so as to become metallic ispolyacetylene. An example of a device according to the disclosure havingone or more Schottky junction is a Schottky solar cell, or ametal-insulator-semiconductor (MIS) Schottky cell.

FIG. 5 illustrates a method of fabricating the device of FIG. 1 throughFIG. 4. A surface of a first electrode 12 is modified such that thefirst anchor group is bonded to the first anchoring group 16. The firstanchor group can be arranged on the first electrode 12 in aself-assembled monolayer. In FIG. 5, the first anchor groups are notillustrated in a self-assembled monolayer in order to reduce the drawingcomplexity. Methods of forming a self-assembled monolayer on theelectrode surface can be employed to bond the first anchoring group 16to the electrode. When the surface to be modified is a metal or a metaloxide, a suitable method for bonding the first anchoring group 16 to thefirst electrode 12 includes, but is not limited to, Tethering ByAggregation and Growth (T-BAG). When a phosphonic acid is used as aprecursor for the anchoring group, the Tethering by Aggregate Growthmethod produces a dense self-assembled monolayer of anchoring groupsthat are covalently bonded to the electrode by phosphonate oxide bondssuch as the bonds shown in FIG. 2. Forming these layers includes theself-assembly monolayer replacing oxygen and hydroxyl groups present onthe surface of the metal or metal oxide. The removal of hydroxyl groupsfrom the surface can be beneficial because the hydroxyl groups cancreate electronic trap states at an oxidized metal interface.

The first organic polymer 18 is formed on the first anchoring groups 16.For instance, a first organic polymer 18 can be polymerized on the firstanchoring groups 16. A suitable mechanism for polymerizing the firstorganic polymer 18 is a ring-opening polymerization (ROMP) such asRing-Opening Metathesis Polymerization. In one example, the firstorganic polymer 18 is formed on the anchoring groups using SurfaceInitiated Ring-Opening Metathesis Polymerization. The polyacetylene andpoly(thienylenevinylene) illustrated in FIG. 2 can both be generatedusing Surface Initiated Ring-Opening Metathesis Polymerization.Additionally, a copolymer including polyacetylene andpoly(thienylenevinylene) arranged as illustrated in FIG. 2 can begenerated using Surface Initiated Ring-Opening MetathesisPolymerization.

In a Ring-Opening Metathesis Polymerization, a driving force for thereaction is the release of ring strain in cyclic olefins. TheRing-Opening Metathesis Polymerization can be catalyzed through theformation of metal-carbene complexes (M=CR₂ or M=CRH where M representsa metal and R represents an organic moiety). The metal-carbene complexcan attack the double bond in the ring structure to form ametallacyclobutane intermediate. The breakdown of thismetallacyclobutane favored the ring-opened product, which relieves thestrain of the cyclic olefin and provides a linear chain that containsthe metal carbene catalyst as the ‘living end.’ The carbene reacts witha carbon-carbon double bond on the next monomer to propagate thepolymerization.

In a Surface Initiated Ring-Opening Metathesis Polymerization, the firstanchoring groups 16 are modified to include the catalyst complex. Forinstance, the first anchoring group 16 can include a carbon-carbondouble bond and, more particularly, a terminal carbon-carbon doublebond. The first anchoring groups 16 are exposed to the catalyst, whichcan form an anchoring metal-carbene complex with the first anchoringgroup 16. As described above, the monomer is introduced to initiate thepolymerization of a linear chain with the catalyst at the terminus. As aresult, the growing polymer chain terminates at a double bonded betweena carbon and a metal center of the catalyst. Accordingly, the catalystremains at the terminal end of the growing polymer chain and the growthoccurs by adding additional monomer to the terminal end of the polymerchain.

Suitable monomers for ring-opening polymerizations include, but are notlimited to, alicyclic compounds. Suitable monomers for Ring-OpeningMetathesis Polymerization include, but are not limited to, cyclicolefins. Suitable catalysts for ring-opening polymerizations and/orRing-Opening Metathesis Polymerizations include, but are not limited to,Grubb's catalyst(1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene)dichloro(phenylmethylene)(tricyclohexylphosphine)ruthenium), (C₄₆H₆₅Cl₂N₂PRu), and Ruthenium,[1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(phenylmethylene)(tricyclohexylphosphine).

The polymerization can be paused by reducing the amount of availablemonomer, eliminating free monomer, or transferring the polymerization toa new environment. When it is desirable for the active layer 10 toinclude the nanoparticles 36, the nanoparticles 36 can be added afterthe polymerization of the first organic polymer 18 is stopped. Thenanoparticles 36 can be added on top of the previously formed firstorganic polymer 18. For instance, the size of the nanoparticles 36 canbe larger than the spacing between the terminal ends of the firstorganic polymer 18 chains in order to reduce substantial penetration ofthe nanoparticles 36 into the spaces between adjacent chains of thefirst organic polymer 18. Suitable methods for adding the nanoparticles36 on top of the first organic polymer 18 includes, but is not limitedto, transfer printing, spin-casting or drop-casting.

After the placement of the nanoparticles 36, the polymerization reactioncan be resumed with the resulting polymer chains extending through theinterstices between adjacent nanoparticles 36. For instance,polymerization techniques including Ring-Opening MetathesisPolymerization and Surface Initiated Ring-Opening MetathesisPolymerization can be resumed by reintroducing monomers to thepreviously formed polymer chains. The newly introduced monomers can bethe same monomers as were previously used to form the first organicpolymer 18. In the method shown in FIG. 5, the newly introduced monomersare second monomers for polymerizing the second organic polymer 22. WhenSurface Initiated Ring-Opening Metathesis Polymerization is employed topolymerize the first organic polymer 18, the second monomers are alsoselected to polymerize by a Ring-Opening Metathesis Polymerizationmechanism that uses the same catalyst as was used to polymerize thefirst organic polymer 18. As a result, the polymerization resumes uponthe exposure of the previously formed polymer chains to the secondmonomers but the resumed polymerization forms the second polymer.

The polymerization of the second polymer can be stopped by exposing thepolymer chains to a chain transfer agent. Chain transfer agents transferthe catalyst from a growing polymer chain to the chain transfer agent.Since the polymerization during a Surface Initiated Ring-OpeningMetathesis Polymerization occurs at the terminal end of the polymerchains, the use of a chain transfer agent results in all or a portion ofthe chain transfer agent being bonded to the end to the polymer chains.This enables one to functionalize the growing surface of the polymericmaterial. As a result, the chain transfer agent can be selected toinclude or consist of a precursor for the second anchoring agent thatbecomes bonded to the terminal end of the polymer chains. In someinstances, the chain transfer agent can also be selected such that thecatalyst or the metal from the catalyst is released from the polymerchains. As a result, expensive catalysts such as ruthenium can berecovered for later use.

In one example, the polymerization is stopped with a diphosphonic acidchain transfer agent such the diphosphonic acid represented by(OH)₂OP(CH₂)_(x)CH═CH(CH₂)_(x)PO(OH)₂ where x is greater than or equalto 1 and/or less than or equal to 20. This diphosphonic acid can replacea double bond between a carbon and catalyst at the terminal end of thepolymer chain with a double bond between the carbon and a secondanchoring group 20 precursor represented by ═CH(CH₂)_(x)PO(OH)₂ where xis greater than or equal to 1 and/or less than or equal to 20.Additionally, the chain transfer reaction produces M=CH(CH₂)_(x)PO(OH)₂where M represents the catalyst or the metal included in the catalyst.The M=CH(CH₂)_(x)PO(OH)₂ can be used as catalyst in a subsequentpolymerization or can be further processed to recover the M in a formthat is suitable for use as a catalyst in a subsequent polymerization.Other examples of suitable chain transfer agents include, but are notlimited to, symmetrical internal olefins or vinyl ethers.

The surface that results from forming the precursor for the secondanchoring group 20 can be metallized to form the second electrode 14.The metallization is performed such that the precursor for the secondanchoring group 20 is converted to the second anchoring group 20. Forinstance, when the surface of the second electrode 14 includes aluminumor aluminum oxide, the second anchoring group 20 precursor representedby ═CH(CH₂)_(x)PO(OH)₂ becomes covalently bonded to the second electrode14 as illustrated in FIG. 2. Suitable methods for performing themetallization include, but are not limited to, atomic layer deposition,thermal evaporation, RF plasma sputtering, wafer-bonding andelectron-beam deposition.

After making any desired electrical contacts, the device resulting fromthe method of FIG. 5 can be hermetically sealed to prevent airdegradation of the active polymer. Suitable materials for sealing thedevice include airtight polymers such as poly(dicyclopentadiene) orpoly(vinyl alcohol co-ethylene).

In one example of the method disclosed in FIG. 5, the first electrode 12includes a layer of fluorine tin oxide (FTO) on a layer of SiO₂substrate as shown in FIG. 2 and a precursor for the first anchoringgroups 16 is represented by CH₂CHCH₂PO(OH)₂. Using the Tethering byAggregate Growth method on these materials produces first anchoringgroups 16 that are attached to the first electrode 12 as shown in FIG. 2and that terminate in a carbon-carbon double bond. The firstsemiconducting polymer is polymerized on the first anchoring groups 16using a Surface Initiated Ring-Opening Metathesis Polymerization whereGrubb's catalyst is the catalyst and the monomer is [18]annulene-1,4;7,10; 13,16-trisulfide. The result of this polymerization is thepoly(thienylenevinylene) illustrated in FIG. 2. After the polymerizationis paused, a layer of nanoparticles 36 is deposited on thepoly(thienylenevinylene) chains by transfer printing. The nanoparticles36 are silver nanoparticles 36 with a diameter of 50-100 nm. The SurfaceInitiated Ring-Opening Metathesis Polymerization is resumed using thesame catalyst and cycloctatetraene as the second monomer. The result ofthe resumed polymerization is the polyacetylene illustrated in FIG. 2.The polymerization is stopped with the diphosphonic acid represented by(OH)₂OP(CH₂)_(x)CH═CH(CH₂)_(x)PO(OH)₂ so as to double bond a terminalcarbon in the polyacetylene to the second anchoring group 20 precursorrepresented by ═CH(CH₂)_(x)PO(OH)₂. The result is metallized withaluminum using thermal evaporation so as to covalently bond the secondanchoring groups 20 to the second electrode 14 as shown in FIG. 2.

The Surface Initiated Ring-Opening Metathesis Polymerization and theRing-Opening Metathesis Polymerization discussed above are livingpolymerizations and/or can be performed under the conditions that makethe polymerization a living polymerization. As a result, the rate atwhich the different polymer chains grow is more consistent than seen intraditional chain polymerization. The similarity in the rate at whicheach chain grows results in chains of very similar lengths. Forinstance, more than 50%, 75%, or 90% of the active polymer chains 24 canhave a distance between the terminal carbons at opposing ends of eachpolymer chains 24 is equal to the average distance between the terminalcarbons +/−50 nm, 25 nm or 10 nm of that average distance.

The above techniques can align the chains as discussed above. Forinstance, in the method discussed above, the polymer chains can be grownon a self-assembled monolayer of first anchoring groups 16. The use ofself-assembled monolayers allows the first anchoring groups 16 to bedensely packed on the first electrode 12. Growing the polymer chains ondensely packed first anchoring groups 16 keeps the polymer chainsdensely packed. Additionally, the consistency in the rate at which eachchain grows effectively causes the polymer chains to be formed one layerat a time. The combination of the dense packing and forming the polymerchains in layers causes the pattern in which the first anchoring groups16 are arranged on the first electrode 12 to be retained through thepolymer chains as discussed above.

While Ring-Opening Metathesis Polymerizations can be performed in liquidphases or in vapor phases, performing the vapor phase may provide evenfurther alignment of the polymer chains. For instance, the rate ofdiffusion of the catalyst in solution is higher than at a vapor/solidinterface. The reduced rate of diffusion in the vapor phase growthreduces the opportunity for the polymer chains to change directionsduring growth. As a result, performing the ring-opening metathesispolymerizations in a vapor phase can further enhance of the alignment ofthe polymer chains. Performing the polymerization in the vapor phaseincludes exposing the device to monomers and catalysts in the vaporphase.

When using the above methodology, there may be no need for the polymersor monomers to include solubilizing side chains because the polymers aregrown directly on the electrode surface and no further processing isnecessary. As a result, in some instances, the monomers and/or resultingpolymers can be unsubstituted and/or exclude sidechains.

The above discussion applies the nanoparticles 36 on the polymer chainsafter stopping the growth of the first semiconducting polymer andstarting the growth of the second semiconducting polymer. As discussedabove, a p-n junction is formed at the interface of the firstsemiconducting polymer and the second semiconducting polymer. As aresult, the p-n junction can be located in the interstices betweenadjacent nanoparticles 36. An entity is positioned in an intersticebetween nanoparticles 36 when a line that contacts two of thenanoparticles 36 also passes through that entity. The two nanoparticles36 contacted by the line are preferably adjacent to one another. Themethod can be modified to move the layer of the nanoparticles 36 toother locations in the active layer 10. For instance, the growth of thefirst semiconducting polymer can be paused, the nanoparticles 36 can beapplied and the growth of the first semiconducting polymer resumed inorder to move the layer of nanoparticles 36 away from the p-n junctionand into the first semiconducting polymer. As a result, the layer ofnanoparticles 36 would be located between the first electrode 12 and thep-n junction. In some instances, the layer of nanoparticles 36 would belocated between the first electrode 12 and the p-n junctions without thep-n junctions being located in the interstices of the nanoparticles 36.Additionally or alternately, the growth of the second semiconductingpolymer can be paused, the nanoparticles 36 can be applied and thegrowth of the second semiconducting polymer resumed in order to move thelayer of nanoparticles 36 away from the p-n junction and into the secondsemiconducting polymer. As a result, the layer of nanoparticles 36 wouldbe located between the second electrode 14 and the p-n junction. In someinstances, the layer of nanoparticles 36 would be located between thesecond electrode 14 and the p-n junctions without the p-n junctionsbeing located in the interstices of the nanoparticles 36. Using thesetechniques, multiple layers of nanoparticles 36 can be present in theactive layer 10. Accordingly, the active layer 10 can include one ormore layers of nanoparticles 36. Different layers of nanoparticles 36can include different nanoparticles 36.

The ability to pause and restart the polymerization also permits theformation of multiple junctions in the active layer 10. For instance, anactive polymer 24 for use in the active layer 10 can be formed using theabove methods to polymerize an organic polymer that serves as anelectron donor, followed by polymerizing an organic polymer that servesas an electron acceptor, followed by polymerizing an organic polymerthat serves as an electron donor. The result is a device having two p-njunctions. The steps can be repeated to form more than two junctionswithin the active layer 10. An organic polymer that serves as anelectron donor in one block of the active polymer 24 can be the same ordifferent from the organic polymer that serves as an electron donor inanother block of the active polymer 24 and/or an organic polymer thatserves as a electron acceptor in one block of the active polymer 24 canbe the same or different from the organic polymer that serves as aelectron acceptor in another block of the active polymer 24. As notedabove, the active layer 10 can optionally include one or more layers ofnanoparticles 36 at different locations along the length of the activepolymer 24.

A suitable thickness for a layer of nanoparticles 36 includes athickness greater than 5 nm, 50 nm, or 100 nm and/or less than 2 μm, 250nm, or 100 nm. A suitable average distance from the first electrode 12or the second electrode 14 to the last carbon in the chain of the activepolymer 24 includes distances greater than 10 nm, 50 nm, or 500 nmand/or less than 1 cm, 1 mm, or 1 μm. Accordingly, the thickness of thelayer of nanoparticles 36 can be less than 75%, 50%, 25% of an averagedistance between the electrode and a carbon located at the terminal endof each active polymer 24 chains. In some instances, the firstsemiconducting polymer has more than 5, 50, or 500 repeating unitsand/or less than 500,000, 50,000, or 5000 repeating units and/or thesecond semiconducting polymer has more than 5, 50, or 500 repeatingunits and/or less than 500,000, 50,000, or 5000 repeating units.

Although the method of FIG. 5 discusses the formation of nanoparticles36 in the active layer 10, these nanoparticles 36 are optional asdiscussed above. The above method can be modified to form deviceswithout these nanoparticles 36 (i.e. FIG. 1) by forgoing the steps wherethe nanoparticles are positioned in the active layer 10.

Although the method of FIG. 5 discusses the active polymer 24 beingformed from the first electrode 12 toward the second electrode 14, thedisclosed method can be performed in reverse. For instance, the methodcan start with the second electrode 14 and work toward attachment of thefirst electrode 12 at the end of the method. As a result, terms likefirst and second do not denote sequence but are employed to distinguishbetween different features.

Example 1

2×2 cm silicon coupons were cleaned with piranha for one hour, rinsedwith DI water, methanol and acetone, and dried under argon. A selfassemble monolayer of pent-5-enyl phosphonic acid was prepared on asurface of the coupons by the TBAG method from a solution in THF. In anitrogen-filled glove box, the functionalized coupon was placed into asolution of 25 mg of the Ru catalyst[1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(3-methyl-2-butenylidene)(tricyclohexylphosphine)ruthenium(II) in 2 mL of toluene, which was heldunder static vacuum for 10 minutes. The coupon was removed and submergedinto fresh toluene, rinsed with ˜10 mL of toluene, and allowed to dry.The coupon was placed in a flat-bottomed Schlenk flask, which wasevacuated to 150 millitorr and backfilled with 5 psi acetylene gas for16 hours. Dark black crystallites were observed by optical microscopy.These crystallites can be contacted with a metal probe tip to provide anexample of a complete device, where the silicon substrate serves as oneelectrode, and the probe tip as the other.

Other embodiments, combinations and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

1. An electronics device, comprising: a first electrode and a secondelectrode; and organic polymer chains that are each covalently linked toboth the first electrode and the second electrode.
 2. The device ofclaim 1, wherein terminal ends of each organic polymer chain arecovalently linked to both the first electrode and the second electrode.3. The device of claim 1, wherein a first portion of each organicpolymer chain is a polymer that is an electron acceptor and a secondportion of each organic polymer chain is polymer that is an electrondonor.
 4. The device of claim 1, wherein the organic polymer chains arealigned with one another.
 5. The device of claim 1, further comprising:a layer of nanoparticles arranged such that at least a portion of theorganic polymer chains extend through interstices between thenanoparticles.
 6. The device of claim 5, wherein the organic polymerchains each includes a p-n junction and at least a portion the p-njunctions are positioned in interstices between the nanoparticles. 7.The device of claim 6, wherein a thickness of the layer of nanoparticlesis less than 50% of an average distance between a carbon at a firstterminal end of each organic polymer chain and a carbon located at aterminal end of each organic polymer chain.
 8. An electronics device,comprising: block copolymer chains that are aligned with one another andthat are positioned on a surface of an electrode; the block copolymerchains each including a first block of a first organic polymer; and theblock copolymer chains each including a second block of a second organicpolymer.
 9. The device of claim 8, wherein the first organic polymer isa semiconducting organic polymer that acts as an electron acceptor andthe second organic polymer is a semiconducting organic polymer that actsas an electron donor.
 10. The device of claim 8, wherein the electrodeis transparent to sunlight.
 11. The device of claim 8, wherein a p-njunction is formed at an interface between the first block and thesecond block.
 12. The device of claim 8, further comprising: a layer ofnanoparticles arranged such that the block copolymer extends throughinterstices between the nanoparticles.
 13. A method of forming anelectronics device, comprising: polymerizing a polymer on an electrodeso as to form chains of the polymer on the electrode; pausing thepolymerization after the polymerization has been started; applying alayer of nanoparticles to the portion of the polymer chains that wereformed before the polymerization was paused; and resuming thepolymerization after applying the nanoparticles.
 14. The method of claim13, wherein the polymerization is resumed such that the polymer chainsextend through interstices between the nanoparticles.
 15. The method ofclaim 13, wherein the nanoparticles have an average diameter greaterthan 5 nm.
 16. The method of claim 13, wherein a first monomer is usedin the polymerization of the polymer before the polymerization is pausedand a second monomer is used in the polymerization of the polymer afterthe polymerization is resumed, the first polymer being different fromthe second polymer.
 17. A method of forming an electronics device,comprising: providing an electrode; and fabricating block copolymerchains on a surface of the electrode such that the chains are alignedwith one another, the block copolymer chains each including a firstblock of a first organic polymer; and the block copolymer chains eachincluding a second block of a second organic polymer.
 18. The method ofclaim 17, wherein the first organic polymer is a semiconducting organicpolymer that acts as an electron acceptor and the second organic polymeris a semiconducting organic polymer that acts as an electron donor. 19.The method of claim 17, wherein fabricating the block copolymer chainson the surface of the electrode includes polymerizing the first block onthe electrode followed by polymerizing the second block on theelectrode.
 20. The method of claim 17, further comprising: bonding theblock copolymer chains to a second electrode such that the blockcopolymer chains are between the electrode and the second electrode.